Coherent light generators – Particular beam control device
Patent
1986-05-15
1987-12-15
Scott, Jr., Leon
Coherent light generators
Particular beam control device
372 38, 372 33, H01S 310
Patent
active
047138190
ABSTRACT:
A laser beam emitted from a semiconductor laser is detected by a PIN type photodiode. A forward bias source or a reverse bias source is coupled to the photodiode through a switch. When a power source is turned on, the switch is switched to connect the forward bias source to the photodiode. A forward bias current is applied to the photodiode. At this time, a driver circuit has not yet been supplying a drive current to the semiconductor laser. With a forward bias current applied, a forward voltage drop is generated across the photodiode. A discrimination circuit compares the forward voltage drop to a reference voltage range. When the forward voltage drop is outside the range, it is determined that the photodiode is abnormal, and the driver circuit is controlled such that no drive current is supplied to the semiconductor laser. When the forward voltage drop is in the reference voltage range, the operation of the driver circuit is started, and the switch is switched to connect the reverse bias source to the photodiode. Therefore, the semiconductor laser is caused to effect intensity modulation oscillation according to an externally supplied modulation signal. The photodiode supplies a photoelectric conversion signal corresponding to the quantity of received light to an APC circuit, so that the output of the semiconductor laser is controlled for stabilization.
REFERENCES:
patent: 4348648 (1982-09-01), Childs
patent: 4479221 (1984-10-01), Kitamura
patent: 4584687 (1986-04-01), Howard
patent: 4604753 (1986-08-01), Sawai
Jr. Leon Scott
Olympus Optical Co,. Ltd.
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